Naphthalimide whitening agents anb
method of making same



U ited taes The present invention relates to new optical whitening agents, particularly to new optical whitening agents comprising novel naphthalimide derivatives, and a method for the manufacture as well as the applications of said optical whitening agents. An object of the present invention is to provide useful novel optical whitening agents. Another object of the invention is to provide a method for economica'lly manufacturing the novel optical whitening agents. Further object of the invention is to provide a method for imparting a remarkable white-enhancing effect to artificial or synthetic organic high molecular weight materials such as textile or plastic materials.

The abovementioned first object of the invention is accomplished by providing new naphthalimide derivatives shown by the following Formula 1:

N-Rr

wherein R denotes an organic group having no dyestuif character and R denotes hydrogen atom or an organic group having no dyestufl' character.

As a result of our extensive studies made for the purpose of obtaining valuable, novel optical whitening agents for various artificial or synthetic organic high molecular weight materials such as textile or plastic materials, we have found such naphthalimide derivatives as shown by Formula 1 entirely satisfactory for achieving our aforementioned objects. Namely, these compounds when dissolved or dispersed in a suitable solvent or when applied to a fitting fundamental material emit a distinctive greenish blue fluorescence in daylight or ultraviolet rays showing a wide absorption in the ultraviolet range. Further, these compounds generally have good stability and exhibit strong affinity with artificial or synthetic organic high molecular weight materials. Hence, the compounds of Formula 1 are able to impart an outstanding and durable optical Whitening effect to the abovementioned materials.

Among the optical whitening agents shown by the above Formula 1 there are cited various naphthalimide derivatives. For example, R in the Formula 1 includes an organic group having no dyestuif character which may be, for example, such alkyl groups of straight chain or branched chain as methyl, ethyl, nor iso-propyl, nor iso-buty'l, nor iso pentyl, nor iso-hexyl, n-octyl, Z-ethyl-hexyl, nor iso-dodecyl, and nor iso-tridecyl. Further, R may be a substituted alkyl group substituted by at least one of hydroxy, alkoxy, aryl, primary amino, secondary amino such as alkyl amino, tertiary amino such as bisalkyl amino and quaternary ammonium such as trialkyl ammonium. They may be, for example, hydroxyethyl, hydroxypropyl, hydroxybutyl, methoxyethyl, ethoxyethyl, ethoxypropyl, propoxypropyl, benzyl, aminoethyl, aminopropyl, N,N-dimethyl-amino-ethyl, N,N- dimethyl-amino-propyl, N-trirnethyl ammonium ethyl, N- trimethyl ammonium propyl, N-triethyl ammomium ethyl, and N-triethyl ammonium propyl. Still further, R may be such aryl group as phenyl and naphthyl or a substituted aryl group substituted by at least one of alkyl, alkoxy, hydroxy, alkoxyalkyl, hydroxyalkyl, amino,

333,834 Patented July 11, 1967 secondary aminoalkyl, tertiaryaminoalkyl, quaternaryammonium alkyl, nit-r0, and halogen. Still further, R may be such cycloaliphatic group as cyclohexyl. Also, R may be, for example, such a group as shown by the formula:

On the other hand, R shown in the Formula 1 denotes either hydrogen atom or an organic group having no dyesturT character. The said organic group may be any of various groups having no dyestuif character that have been referred to as R in the foregoing.

The embodiments of the optical whitening agents according to the present invention will be further illustrated by reference to the examples given below.

The optical whitening agents according to the invention are economically manufactured by the methods as follows:

The most practical method for manufacturing the optical Whitening agents of the invention comprises etherifying 4-rnercapto-naphthalimide or its derivative, which is indicated by the following formula:

Ms 0 o wherein M denotes hydrogen atom or alkali metal, and R is of the same significance as in Formula 1, by the use of an etherifying agent having no dyestuif character.

Among 4-mercapto-naphthalimides indicated by the aforementioned formula, there are 4-mercapto-naphthalimides or alkali salts thereof, e.g., sodium salts and potassium salts and their N-substituted compounds. The said N-substituted compounds have an organic group having no dyestulf character as the N-substituents which have been explained as R in Formula 1. As regards the etherifying agents to be used for etherifying the 4-mercaptonaphthalimides, strong acid esters having no dyestufif character may first be mentioned. The representative examples of said strong acid esters are such alkyl sulphate as dirnethyl sulphate or diethyl sulphate. As the etherifying agents may also be cited organic compounds containing an active halogen atom, which may be for example such alkyl halides as methyl iodide, ethyl iodide, methyl bromide, ethyl bromide, butyl bromide, methyl chloride, and ethyl chloride or such substituted alkyl halides as ethylene chlorohydrin, and l N,N dimethylamino-Z- chloro-ethane, benzyl chloride or such halogenated aryl derivatives as p-nitrochlorobenzene and 4-chl0ro-N- methyl-naphthalimide. Also, such esters of organic sulphonic acid as methyl ester of p-toluene sulphonic acid or ethyl ester of p-toluene sulphonic acid may be employed as the etherification agent. The etherification reaction may be efficiently performed in the presence of such alkaline substances preferably as alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbontes, alkali metal phosphates, alkali metal silicates and alkali metal acetates. The etherification reaction is ef fected generally at temperature in a range from about 20 to 200 C. while using preferably such inert diluents as water or alcohols. In accordance with such a method the desired product as indicated by Formula 1 is produced. Generally, the reaction product is allowed to precipitate at room temperature and subject to subsequent filtration for separation. Alternatively, the reaction liquor is either acidified or concentrated by way of distilling the diluent ofi the reaction liquor so that the reaction product is precipitated and it is then separated by filtration. The purity of the reaction product thus obtained is generally high enough but the purity may be enhanced, if required, either by washing of said reaction product employing an alkaline aqueous solution or by recrystal- 4- purpose, a treating bath is made up by way of uniformly dispersing the optical whitening agents in Water by use of a suitable dispersing agent and or wetting agent, said bath being used for dipping or padding polyester textile lization of said reaction product employing a solvent. material at a temperature up to 100 C. In some cases, The 4-mercapto-naphthalirnides employed as the startso-called carrier dyeing method may be carried out whereing materials in the abovementioned methods may be in such carrier as chlorobenzene series is employed. manufactured in a more advantageous manner from eco- Also so-called high temperature dyeing or thermosol nomical point of view by a method in which 4halogenoprocess to be employed for dyeing polyester textile manaphthalimides as indicated by the following formula: 16 t ini i applicable a the method of treatment according to the invention. Polyester textile material thus treated emits greenish blue fluorescence in daylight or ultraviolet /NR2 rays. Hence, a remarkable Whitening effect i imparted 00 while neutralizing the yellowish tint of textile material. wherein X denotes a halogen atom, and R is of the same op 5 whlftenmgtlagents i f emclialmly i f significance as in the aforementioned Formula 1, is caused vancius types 0 Synt. em: or f clal 6 matena S mto react with alkali metal sulphides as indicated by M s i i Such texflle matenfqls as M denoting an alkali metal and y a number from 1 to 5, ominle and Polyvinyl chloflde; Such mtrogen'confalmng in the presence of such an inert solvent as water or an m mammals as Polyannde; such Polyolefin textlle alcohol or a mixture thgreof at a tempsrature from terrals as polypropylene; and such cellulose esters as celluto lose acetate. The optical Whitening agents according to the The f ti d 4 halogeno naphthalimides may be invention are also applicable to whiten such moulded mamanufactured in an economical manner in accordance tefials as Sheet, P board, P p and block, with any of two processes as shown by formulae which 25 Which are made of Various Synthetic artificial follow; resins. For example, mixing the optical whitening agent (i) MOgS- oo RPNH? MOaS- oo 0 NRa 00 00 (E10) EX +MXO;

\ x no NR2 (h) RzNH2/ C 0/ MOJS- C0 HX+MXO3 X GO O 00/ (1120) CO/ wherein M denotes hydrogen atom or an alkali metal according to the invention with such synthetic resin as and X a halogen atom. A0 polystyrene or polymethyl methacrylate followed by such Further, the optical whitening agents as shown by moulding as extrusion and injection results in producing a Formula 1 may be manufactured in accordance with a transparent moulded material, which emits greenish blue process in which a compound as indicated by formula: fluorescence. A brilliant coloured material may be obtained by blending a suitable colouring agent in the above- Y Co mentioned mixing. The optical whitening agents are also NR2 applied to white-enhancing treatment of variou moulded 00 materials composed of synthetic resins such as polyvinyl wherein Y denotes a sulpho group, a salt thereof, nitro group or halogen atom, and R is of the same significance as in Formula 1 is condensed with a mercaptan as indicated by R SH, R being of the same significance as R in the aforementioned Formula 1.

Still further, the optical whitening agents as indicated by the aforementioned Formula 1 may be manufactured by wherein R is of the same significance as in the aforementioned Formula 1 or an ahydride thereof with a compound as indicated by formula R NH R being of the same significance as R in the aforementioned Formula 1.

The novel optical whitening agents as indicated by Formula 1 exert remarkable whitening effect on various materials, particularly on artificial or synthetic organic high molecular weight materials by fixing, penetrating, mingling, or adhering.

The treatment of such polyester textile material as polyethylene terephthalate is generally performed in accordance with conventional methods for dyeing this textile material by using an aqueous dispersing medium containing the optical whitening agent of the invention. For this chloride, polyacrylate, polyester, polycarbonate, polyurethane, polyamide, and polyolefin. As a result of these treatments an excellent white-enhancing effect is always bestowed although the degree is not exactly the same. The optical whitening agents in accordance with the present invention may be employed in a mixture with such an optical whitening agent that is indicated by a formula which follows:

wherein R and R each are of the same significance as in the aforementioned Formula 1. Such a mixture gives an optical whitening effect which emits fluorescence having more bluish tint.

The white-enhancing treatments by use of the optical whitening agents according to the invention may be carried out by methods other than the abovementioned methods. For example, mixing of the optical whitening agents according to the invention may be carried out in a suitable step during the process of manufacturing textile material or synthetic resin. Further, it may be feasible to spread on the surfaces of moulding material a suitable solvent in which the optical whitening agents are contained.

Some preferred embodiments of the invention will be described in detail wherein the examples given are for the purpose of illustrating preferred embodiments only and not for the purpose of limiting the same. The part in the following denotes the portion by weight unless otherwise specified. The melting point of the compounds shown in the following examples is uncorrected.

Example 1 24.6 parts of N-methyl-4-chloro-naphthalimide are added to a solution consisting of 15.6 parts of sodium sulphide (Na S), 100 parts of water and 200 parts of methanol, and heated under stirring to efiect reaction for 4 hours at the boiling point. Upon completion of the reaction the reaction liquor is cooled to about 50 C., and to which added is a solution composed of 20.8 parts of sodium bisulphite and 40 parts of water, followed by filtration to remove precipitate. The filtrate contains 25.2 parts of sodium salt of N-methyl-4-mercapto-naphthalimide. The filtrate is acidified by adding thereto a quantity of dil. HCl, filtered to take out precipitate, rinsed with cool water until the precipitate becomes neutral, and dried under reduced pressure. Thus obtained are 19.5 parts of N-methyl-4-mercapto-naphthalimide of melting point from 214.5 to 216.2 C. The analytical values of this product closely approximate the calculated values as indicated below:

Calcd. for C H NO S: C (percent), 64.18; H (percent), 3.73; N (percent), 5.77; S (percent), 13.17. Found: C (percent), 60.94; H (percent), 3.37; N (percent), 6.20; S (percent), 13.28.

24.6 parts of N-methyl-4-chloro-naphthalimide are added to a solution containing 18.8 parts of a mixture of sodium sulphide (Na s) and sodium disulphide (Na S in 300 parts of water and heated under stirring to effect reaction for ten hours at a temperature from 95 to 98 C. Upon completion of the reaction, the resultant product is subject to the same treatment as in Example 1 to obtain 19.0 parts of N-methyl-4-mercapto-naphthalimide.

Example 3 28.8 parts of N-n-butyl-4-chloro-naphthalimide are added to a solution comprising 22.0 parts of sodium disulphide, 110 cc. of water and 200 parts of ethanol and heated under stirring to effect reaction for 4 hours at the boiling point. Upon completion of the reaction, 250 parts of water are added to the reaction mixture to which further added is an aqueous solution comprising 20.8 parts of sodium bisulphite and 40 parts of water, and filtered to remove precipitate. The filtrate contains 20.0 parts of sodium salt of N-n-butyl-4-mercaptonaphthalimide. The filtrate is subject to the same treatment as in Example 1 to obtain 14.3 parts of N-n-butyl-4-mercapto-naphthalimide of melting point from 116.5 to 118.0 C. The same product is obtained by employment of N-n-butyl-4- bromo-napht-halimide in place of N-n-butyl-4-chloronaphthalimide employed in this example. The analytical values of this product closely approximate the calculated values as indicated below:

Calcd. for C H NO S: C (percent), 67.34; H (percent), 5.27; N (percent), 4.91; S (percent), 11.22. Found: C (percent), 66.60; H (percent), 5.25; N (percent), 4.88; S (percent), 11.27.

Example 4 12.0 parts of sodium hydroxide and 26.5 parts of a sodium salt of N-methyl-4-mercapto-naphthalimide manufactured in accordance with the method of Example 1 or 2 are dissolved in 500 parts of water. To the resulting solution are added 25.2 parts of dimethyl sulphate and stirred for 10 hours at a temperature from 20 to 30 C. Upon completion of the reaction, the reaction mixture is filtered to remove the precipitate. The filtered cake is rinsed in succession by sodium carbonate aqueous solution and water until the cake becomes neutral, and dried to obtain N-methyl-4-methylthio-naphthalimide with theoretical yield. Recrystallization of this product by use of acetic acid results in obtaining a pure product of melting point from 219.5 to 220.0 C. The analytical values of this product closely approximate the calculated values as shown below:

Calcd. for C H NO S: C (percent), 65.3; H (percent), 4.29; N (percent), 5.45; S (percent), 12.45. Found: C (percent), 63.98; H (percent), 4.21; N (percent), 5.30; S (percent), 12.10.

The same product as mentioned above is obtained 'by use of either 15.9 parts of sodium carbonate or 20.7 parts of potassium carbonate in place of 12.0 parts of sodium hydroxide employed in this example.

This product emits distinct fluorescence of greenish blue tint in such organic solvents as methanol or acetic acid. Further, this product gives an excellent optical white-enhancing effect to organic high molecular weight materials.

Example 5 12.0 parts of sodium hydroxide are dissolved in a solution consisting of 26.5 parts of sodium salt of N-methyl- 4-mercapto-naphthalimide manufactured by the method in Example 1 or 2 and 500 parts of water, 37.2 parts of methyl ester of p-toluene sulphonic acid are added thereto, and stirred for 2 hours at a temperature from 20 to 30 C. to effect subsequent reaction for 2 hours at C. Upon completion of reaction, the reaction product is cooled and filtered to remove the precipitate, which is washed by water and dried to obtain with theoretical yield N-methyl-4-methylthio-naphthalimide of the same grade as in Example 4.

Example 6 12.0 parts of sodium hydroxide are dissolved in an aqueous solution comprising 26.5 parts of sodium salt of N-methyl-4-mercapto-naphthalimide manufactured by the method in Example 1 or 2 to which 41.2 parts of n-butyl iodide are added and heated to cause reaction for 2 hours at C. Upon completion of the reaction, the reaction product is cooled and filtered to remove the precipitate. The filtered cake is rinsed in succession with methanol and water, and dried to obtain with theoretical yield N-methyl-4-n-butylthio-naphthalimide. The recrystallization of this product by use of acetic acid results in obtaining a pure product of melting point from 101.0 to 102.5 C. This material emits a distinctive fluorescence of greenish blue in methanol or acetic acid, and imparts an excellent optical white-enhancing effect to organic high molecular weight materials.

Example 7 30.7 parts of sodium salt of N-n-butyl-4-mercaptonaphthalimide manufactured by the method in Example 3 and 12.0 parts of sodium hydroxide are dissolved in 500 parts of water to which 25.2 parts of dimethyl sulphate are added, and stirred for 10 hours at a temperature from 30 to 40 C. Upon completion of the reaction, the reaction mixture is subject to the same treatment as in Example 4 to obtain with theoretical yield N-n-butyl-4- methylthio-naphthalimide of melting point above 330 C. This material emits a remarkable fluorescence in methanol or acetic acid, and imparts an excellent optical whiteenhancing efiect to various kinds of organic materials.

Example 8 To a solution comprising 400 parts of water and parts of methanol are added 29.5 parts of sodium salt of -(2'-hydroxy)ethyl-4-mercapto-naphthalimide, which is obtained by reacting N-(2'-hydroxy)ethyl-4-chloro-naphthalimide with sodium sulphide in accordance with the method in Example 2, and further 12.0 parts of sodium hydroxide. 50.4 parts of dirnethyl sulphate are added to the resultant solution, stirred for hours at a temperature from 20 to 30 C., and caused to react for 4 hours at 85 C. Upon completion of the reaction, the reaction mixture is subject to the same treatment as in Example 4 to obtain with theoretical yield N-(2'-hydroxy)ethyl-4- methylthio-naphthalimide of melting point from 176.8 to

The analytical values of this product closely approximate the calculated values as shown below:

C H N S (percent) (percent) (percent) (percent) Calctl. for CrsHuNOzS 6'2. 75 4. 53 4. 88 11.15 Found 62. 00 4. 50 4. 92 11. 13

This material emits a remarkable fluorescence in organic solvent, and imparts an excellent optical whiteenhancing effect to various kinds of organic materials.

Examples 9 to 11 listed in column C.

- O 0 Example 17 1 part of N-methyl-4-methylthio-naphthalimide manufactured by the method in Example 4 is mixed with 2 parts of dispersing agent such as a condensate of naphthalene- Z-sulphonic acid with formaldehyde. The mixture is pulverized into easily dispersible powder. The powder is dispersed in 30,000 parts of water to prepare a treatment bath. 150 parts of carrier (chlorobenzenes) are added to the bath in which 1,000 parts of polyester textile material are treated at a temperature from 98 to 100 C. for 2 hrs. The treated textile material is subjected to soaping in 10,000 parts of aqueous solution containing 30 parts of anion surface active agent at 90 C. for 15 mins. and then rinsed and dried. Thus the polyester textile material has been imparted a remarkable whitening effect with a good fastness. The same results as in this example were obtained in the case where the compounds obtained by the methods in Examples 6 to 16 were used.

Example 18 1 part of N methyl 4 methylthio naphthalimide is 'mixed with 2 parts of dispersing agent constituting a con- Objective product Meltmg point, 0.

Ex. 9 Dimcthyl sulphate sodlium salt of 4-mercapto-naphthalinlt-met-hylthio-naphthalimide 285.2-288.8

1 0. Ex. 10.-- tlo Sodium salt of N-(N-N-dimetl\yl- N-(N-N-dimcthylamino) propylt- 196. 0-201. 5

amino) propybtmcrcapto-naphthalimmcthylthio-naphtlialimidc. l e. Ex. 11. do Sodium salt of N-pheuyl-4-mercapto- N-pheny1-4-methyltliio-naphthaliniide 2G9. 8-2112 naphthalimide.

Note.-In Examples 10 and 11, the reaction continues for 10 hours initiating at a temperature from to 0. followed by further reaction for 0.5 to 4 hours at a temperature from to 0.

Examples 12 to 16 An etherifying agent and a starting mercapto-naphthalimide compound listed, respectively, in columns A and B are caused to react in accordance with the method described in Example 6 to yield a novel optical whitening agent listed correspondingly in column C in the following table:

The treated textile material is then subjected in sequence to soaping, rinsing, and drying as in Example 17. Thus remarkably whitened polyester textile material is obtained. Any of various compounds in Examples 6 to 16 may be used for performing the same treatment as in the present example to obtain similarly whitened polyester textile material as in this example.

Ob cctrve product Melting point, 0.

Ex. 12 Ethylene ehlorohydrln Sodium salt of N-methyl- N-methy1-4-(2-hydroxy) ethylthidnaphthalimide 127. 5-131. 5

4-mercapto-naph- V thalimide. Ex. 13 N-bll-dirrethyl-ethyl- 1 N-rnethyl--(N-N-d1methyl) ethylthio-naphthalimide 121. 8-124. 0

c 1 on e. Ex. 14 Benzylchlorida. do N-methyl--benzylthio-naphthalimide 17s. 8-179. 5 Ex. 15 p-nitro-chlorobenzenc Sodium salt of N-rnethyl- N-methyM-(mrtro) phenylthio-naphthalimide 237. 5-238.5

4-rnercapto-naphthalimide.

O C -S C O Ex. 16 N-methyl--chloromaphdo H3CN N-CH 0-303 2 tlialimidc O C Norm-In Examples 15 and 16, the reaction continued for 8 hours at a temperature from 95 to C.

Example 19 1 part of N-methyl-4-methylthio-naphthalimide is dispersed in 30,000 parts of Water to prepare a treatment bath as in Example 18. In the bath are immersed 1,000 parts of cellulose acetate textile material and heated at 85 C. for 1 hr. Then, thus treated textile material is subjected to soaping at 50 C., rinsing and drying. Thus, to the treated textile material has been imparted a remarkable whitening eitect.

1,000 parts of polyamide textile material or polyacrylonitrile textile material in place of cellulose acetate material may be subjected to the same treatment at 100 C. as in this example to impart to the respective textile material a remarkable whitening effect. Further, the whitening of these textile materials is efiected also in the case where any of compounds in Examples 6 to 16 is used.

Example 20 A mixture of 1 part of N-methyl-4-methylthio-naphthalimide and 2 parts of dispersing agent employed in Example 18 is dispersed in 15,000 parts of water to prepare a treatment bath as in Example 18. In the bath are immersed 500 parts of polypropylene textile material followed by heating at 98 to 100 C. for 1.5 hr. and then soaping, rinsing, and drying. Thus a remarkable whitening is imparted to polypropylene textile material.

Example 21 Example 22 A mixture of 2 parts of N-methyl-4-methylthio-naphthalimide and 10,000 parts of polystyrene resin pellet is kneaded at 190200 C., and then moulded into a plate by using an injector. Thus a transparent plate is obtained which emits outstanding blue fluorescence. By adding 20 to 50 parts of titanium dioxide in the course of the aforementioned kneading a white-enhanced plate is obtained. Similar eflect is brought about in the case where any compound in Examples 6 to 16 is used. Further, similar whiteenhancing is also imparted to polymethyl methacrylate resin, polyvinylchloride resin, polyamide resin, polyester resin, and polycarbonate resin as used in place of polystyrene resin in this example.

What we claim is:

1. The compound NCH N-methyl4 methylthio-naphthalimide 2. The compound CH3 (CH2) S C O NCHJ N-methylA-n-butylthio-naphthalimide 3. The compound N-n-bu tyl-4-methylthio-naphthalimide 4. The compound CHaS- CO N(CH2)2OH 00 N- Z-hydroxyethyl) -4-methylthio-naphthalimide 5. The compound -methylthiomaph thalimide 6. The compound N-(-N,-N-dimethylaminopropyl)-4-methyltl1i0-naphthalimide Npheny1-4-methylthiomaphthalimide 7. The compound 8. The compound =Nmethyl4- (2-hydroxyethy1thi0)-naphthalimicle 9. The compound N(CH2)2S C O NCH3 CH3 N-methy1-4 (N,N-dirnethylaminoethylthio -naphthalimide 10. The compound .N-me thyl-et-benzylthi0-naphthalimide 11. The compound NOOS o0 NCHa 00 .N-methyl-- 4-ni-trophenylthi0) -nap11tha1imide 12. The compound (References on following page) 11 12 References Cited OTHER REFERENCES UNITED STATES PATENTS Fuson, Organic Chemistry, Wiley, 1941, pages 62-3 1,625,826 4/1926 Schmidt 260 281 felled 2,231,495 2/1941 Eckert et a1. 260281 5 2,878,138 3/1959 Rave et a1. 117-335 ALEX MAZEL, v Examine"- 2,980,549 4/1961 Craig 117-435 HENRY R. JILES, NICHOLAS S. RIZZO, Examiners.

FOREIGN PATENTS DON M. KERR, D. G. DAUS, Assistant Examiners.

517,630 8/1938 Great Britain. 

1. THE COMPOUND 